As the aircraft carrier HMS Illustrious and the assault ship HMS Bulwark headed towards the eastern Mediterranean, the advice from the Foreign Office to the estimated 10,000 Britons in Lebanon last night was to stay put. "It is not safe to try to leave. Keep a low profile, keep in touch with the embassy and listen to English language radio stations," officials said.

But the Foreign Office also advised Britons to be prepared for departure at short notice. Officials said any evacuation plans - whether by land, sea or air - depended on a ceasefire and its timing. "It is early days. The advice is to do nothing until the security situation has eased," said a Foreign Office official.

One London restaurateur told how his British wife and children were stranded in Beirut after visiting relatives. The man, who manages a Lebanese restaurant, said: "You can't concentrate on anything because you are afraid of what is going to happen for them."

Some of the British citizens are permanent residents in Lebanon. There are a similar number of people with dual British-Lebanese nationality.

Clair Vainola, 31, a drug counsellor from Newcastle working in Beirut, spent last night on a small yacht moored in a marina close to the US embassy in the hope that the site would be safe from Israeli bombs.

She told the BBC: "The only thing I can do is wait and hope that I get out alive. The worst moment is when I hear planes going over, when I see buildings going up in smoke knowing people are being killed and I am powerless to do anything."

Despite news of the British ships heading for the area she was pessimistic. "I haven't heard a dicky bird from the British embassy. What comfort is that to me?"

Norwegian citizens were evacuated from Beirut yesterday in five coaches draped with large Norwegian flags to make them recognisable from the air.

The US, which has about 25,000 citizens in Lebanon, said it had not finalised any plans, but there were reports last night that a handful of Americans, including a sick child, had been evacuated to Cyprus by a US Marines helicopter. The French prime minister, Dominique de Villepin, said "sea and air facilities" would be made available for any of France's 20,000 citizens wishing to leave Lebanon.

HMS Illustrious and HMS Bulwark are unlikely to reach the Lebanese coast for two days, the Ministry of Defence said. However, evacuating thousands of people by ship and helicopter will be a huge and lengthy task